Hello H.,
My son is almost 6 weeks old. We breastfed from the start, but due to difficulties we decided to pump and feed at 2 weeks. My son uses the breast only as a pacifier to soothe himself, but receives his nutrition from the bottle.
At first my supply could not keep up with his demand and I very reluctantly supplemented with formula. It was agonizing for me, but better he eat something than nothing at all. However, with consistent pumping and Mother's Milk Tea he is now exclusively fed expressed breast milk and I have an overabundant supply of milk! In fact I end up freezing much of it. It took less than 2 weeks for my supply to catch up. Here is what worked for me:
1) Make sure you are eating a well-balanced diet and drink LOTS of water. My doctor's office said a gallon a day!
2) Try Mother's Milk Tea 3-5 times daily. Can be found at Whole Foods, Vitamin Shoppe, or other health food stores.
3) Along with pumping every 3 hours, make sure you pump everytime he feeds. So if she feeds every 2 hours, you pump every 2 hours. That way you are mimicking the pattern she would take at the breast and your supply will keep up with his demand. This is especially important when she goes through a growth spurt and wants to feed every hour. Once your supply catches up, you can pump on a more regulated schedule.
4)Try Power Pumping - pick an hour at night and pump for 10 minutes, then break for 10 minutes, pump for 10 minutes, break for 10 minutes and then pump for another 10 minutes. The whole process will take one hour and you will be pumping for a total of 30 minutes. Try this for three nights in a row at about the same time and you should see an increase in supply within 48 hours. You can try this tactic up to once a week. Don't do it everyday! You will exhaust yourself and probably damage your nipples.
5) Lots of skin-to-skin contact. Your hormones will respond to the contact with the baby and stimulate milk production.
6) Wear your baby around the house. Again, same concept as skin-to-skin. The increased contact by carrying your baby with you in a sling or other baby carrier should help activate those hormones. It may be difficult with your back problems though, but any increased contact with the baby should help.
I hope this works for you, but talk to your doctor to see if he/she has any suggestions. It's a harder road we both chose, vs. straight breastfeeding or formula feeding but well worth it! I know from my point of view, there is a lot of support out there for mothers who want to breastfeed (if you know where to look) and it seems to be the societal norm to formula feed. There aren't any "groups" out there for women like us and it seems both sides would want to push us in the other direction. Be proud of the fact that you are working hard to provide what is best for your baby despite your back pain. It will pay off in the end!
Good luck!
P.S.
Be careful what type of storage you select for your breastmilk. Glass kept in the refrigerator tends to have the leukocytes (the cells that transfer your immunity to your baby) stick to the sides; however, glass is good for freezer storage. If you are going to freeze in plastic bags, make sure you use those specifically designed to store breast milk in order to preserve the fat and antibodies. As much as possible, give your baby refrigerated vs. frozen milk as you lose some benefits in freezing milk. However, I am sure frozen breast milk is still better than formula. For people who breastfeed straight from the "tap" so to speak, this is not much of a concern because expressed milk only represents a portion of the baby's diet. For us the proper storage is essential.